Multiple rheostat assembly



March 17, 1970 v cs. E. LEMON 3,501,733

MULT IPLE RHEOS TAT AS SEMBLY Filed June 12, 1968 2 Sheets-Sheet 1INVENTQR. GEORGE E. LEMON F I G. 7

AGENT .March 17, 1970 I ,G. E. LEMON 3,501,733

MULTIPLE RHEOSTAT ASSEMBLY Filed June 12, 1968 2 Sheets-Sheet 2 27A 30 I29A INVENTOR.

GEORGE E. LEMON BY AGENT United States Patent 3,501,733 MULTIPLERHEOSTAT ASSEMBLY George E. Lemon, 286 Lora Ave., Youngstown, Ohio 44504Filed June 12, 1968, Ser. No. 736,453 Int. Cl. H01c /00 US. Cl. 338-1319 Claims ABSTRACT OF THE DISCLOSURE A multiple rheostat assembly forcontrolling a number of related functions, such as the speeds of thedrive rolls of a strip rolling mill. A number of horizontal frames eachhaving a contact blade pivotally connected to one end of the frame arevertically stacked. Associated with each horizontal frame is acylindrical drum having a plurality of resistor elements of differingvalues. The drums are positioned so that the resistor element on thebottom of the drum contacts the blade of the corresponding horizontalframe. The drums are carried by a vertical frame which slides on theside rails of the horizontal frame and the drums may be simultaneouslyrotated to bring different value resistor elements into contact with thecorresponding blades.

This invention relates to a multiple rheostat and more particularly to amultiple rheostat in which each of the rheostats is proportional to theothers and in which the proportions may be varied. Such a multiplerheostat is of particular value in the controlling of the finishingstands of strip rolling mills.

In the production of strip from steel billets, there are providedseveral (usually four) roughing stands which receive heated billets froma furnace and which effect an initial reduction in thickness of thebillet. The resulting slab or bar is then passed to the finishing milltrain, which may, for example, consist of six fourhigh mill stands, eachof which effects a further reduction in thickness of the slab, theresult being a strip of precisely controlled and uniform thickness orgage. It is readily apparent that, in order to prevent cobbles ortearing of the strip during the rolling operation, the individual standsmust be run at successively higher speeds from the first or entrancestand to the last or exit stand. Further, these speeds vary with thethickness of the incoming slabs, the amount of reduction effected byeach stand, and the dc sired exit gage. In order to produce strip havinguniform physical properties it is necessary to maintain the temperatureof the strip within certain limits. This is accomplished by varying thetotal length of time the strip is passing through the mill. Thus, if,for example, an incoming slab is somewhat cooler than desired, it isnecessary to shorten the rolling time by increasing the speeds of allthe stands of the rolling mill.

Presently employed speed control systems are such that the speed of eachstand is adjusted independently of the remaining stands thus requiringan appreciable length of time for the adjusting of the speeds of theentire finishing mill and requiring considerable computation by theoperator to determine the correct speed of each stand thus increasingthe possibility of error.

It is the primary object of the present invention to provide an improvedmultiple rheostat assembly which allows simultaneous, proportionalcontrol of the rheostats. A further object of the invention is theprovision of such a multiple rheostat assembly which permitssimultaneously vemier adjustment of the rheostats without altering theratios between the rheostats. Another object of my invention is theprovision of a multiple rheostat in which the ratios between therheostats may be varied. It is also an object of my invention to providea multiple 3,501,733 Patented Mar. 17, 1970 rheostat which may be usedin the control of the speed of the finishing stands of a strip rollingmill.

The above and other objects and advantages of my invention will becomeapparent upon consideration of the following specification and theaccompanying drawing wherein there is shown a preferred embodiment of myinvention.

In the drawing:

FIGURE 1 is a plan view of the device of my invention;

FIGURE 2 is a front elevational view of the device of FIGURE 1;

FIGURE 3 is a fragmentary, longitudinal sectional view, taken along theline III'III of FIGURE 1;

FIGURE 4 is a fragmentary, transverse sectional view, taken along theline IV -IV of FIGURE 2;

FIGURE 5 is a plan view, on an enlarged scale and partially in section,of the resistor drum used in the device of FIGURE 1;

FIGURE 6 is a fragmentary, transverse sectional view, taken along theline VIVI of FIGURE 5; and

FIGURE 7 is a fragmentary, transverse sectional view, taken along theline VIIVII of FIGURE 1.

I provide a plurality of horizontal frames 10A-Feach having a front rail.11, rear rail 12, and side rails 13. The frames 10A-F are supported, inuniform spacing, by vertical rails 14. The side rails 13 which areconductive are insulated from the front and rear rails 11 and 12 andfrom the vertical rails 14 by insulating pads 15 so that each of theside rails 13 is electrically separated from the remainder of the frame.Each of the side rails 13 is also provided with a terminal 16. Pivotallymounted on a vertical rod 17 carried by projections 12 of the rear rails12 are a plurality of bars 18A-F, one for each of the frames -10AF. Eachof the bars 18 has a rigid base 19, preferably of an insulatingmaterial, and a bladelike conductor 20 on its upper surface. A terminal21 is provided for each of the conductor blades 20. The bars 18 aresupported at their rear ends by the projections 12' and spacers 22 onthe rod 17 and at their front ends by the rails 11 in such manner thatthe upper surfaces of the blades 20 are parallel to the planes definedby the side rails \13. Each of the bars 18A- F is provided with anupwardly extending lever 18A'- to permit the bar to be moved from thetop of the stacked horizontal frames.

Slideably mounted on the side rails 13 of the fixed frame assembly is avertical frame 23 consisting of a pair of end plates 24 to which arefastened shoes 25A-F which slide, respectively, on the rails 13A-F andwhich have upwardly projecting portions 25. Corresponding pairs of theshoes 25 are joined to one another by pairs of side plates 26. The shoesare insulated from the end plates 24 and side plates 26. A resistor drum27 (to be more fully described hereinafter) has its end shafts 28, 29journaled in the projections 25 of each of the pairs of shoes 25A-F.Each of the shafts 29A-F is provided with suitable pulleys and belts 30or gears so that all of the shafts 29A-F may be rotated simultaneously.The shaft 29A extends beyond the shoe 25A and is provided with a wheel31' to permit the operator to rotate the resistor drum 27A and, throughthe belt 30, the drums 27B-F.

Each of the drums 27 consists of a cylindrical, nonconductive bodyportion 32 having a plurality of longitudinal slots 32 uniformly spacedon its cylindrical outer surface. A resistor element 33 is provided ineach of the slots 32' and has its ends connected to disks 34 and 34'which are, in turn, connnected to the shafts 28 and 29. The drums 27 areso positioned that the resistor element 33 in the bottom slot 32 of thedrum contacts the blade 20 of the corresponding bar 18. The resistorelements 33 3 are, preferably, arranged in a uniform order of varyingresistivity.

When the device of my invention is used to control the speed of a striprolling mill, one horizontal frame and associated resistor drum is usedin conjunction with each of the stands of the mill, the rheostat beingconnected in place of the rheostat normally provided in the operatorspulpit and connected by the terminals 16 and the terminal 21 to thedrive motor control circuit.

Suitable markings 35 may be provided on the front rail 11 of theuppermost horizontal frame A for positioning the levers 18A'F and,consequently, the bars 18AF. Likewise markings 36 may be provided on theside rails 13 of the frame 10A for positioning the vertical frame 23 andthe resistor drums 27.

In the embodiment shown, the markings 35 and 36 are specificallydesigned to facilitate the use of my device in controlling the finishingstands of a strip rolling mill. The markings 35 indicate the ratio ofthe speeds of the drive rolls of the stands. It has been found that apreferred ratio for a six stand finishing mill is 3210;:30: 40:45 andthe levers 18A are positioned according to this ratio. If it should benecessary to operate the mill with less than the normal six stands, thebars associated with the stands being operated may be repositioned so asto provide the optimum speed ratio in that situation.

The marking 36, in the illustrated embodiment, indicate the exit gagesof the strip being produced by the mill and these markings are sopositioned that, when, for example, the vertical frame is in registrywith the .140 markings, the speeds of the stands of the mill will be theoptimum ones for rolling strip having this finish gage. If it becomesnecessary to increase or decrease the speed of the rolling operation dueto variation in the temperature of the incoming slab or to otherfactors, the speed can be raised or lowered by rotating the drums 27 tobring a resistor element 33 of greater or less resistance per unit oflength into contact with the blade 20 without disturbing the gagerelated setting of the vertical frame 23 or the speed ratio determinedby the positions of the bars 18. Suitable markings may be provided onthe wheel 31 to indicate the percentage increase or decrease from normalspeed resulting from the selection of a dilferent resistor element.

While the invention has been described with particular reference to thecontrol of the speed of strip rolling mill finishing stands it will bereadily apparent that the device of my invention is not limited to suchuse and may advantageously be employed in any situation where it isdesired to control a number of related operations by means of rheostatsoperating in a ratio, especially where it is desired to vary the ratio,and where it is also desired to allow variation without disturbing thesetting of one of the primary variables. It will also be apparent thatwhile the bars 18 and contact blades 20 are shown as being straight,they may be curved if desired to provide different ratios. Further, thenumber of horizontal frames provided and, therefore, the number ofoperations controlled may also be varied.

As these and other changes may be made in and to the illustratedembodiment of my invention without departing from the spirit thereof,reference should be had to the appended claims in determining the truescope of my invention.

I claim:

1. A multiple rheostat assembly, comprising:

( 1) a plurality of horizontal frames in spaced, vertical relationshipto one another, each frame havin (a) a front rail, I

(b) a rear rail,

(0) a pair of conductive side rails, said side rails being insulatedfrom said front and rear rails, and

(d) a contact bar, said bar being connected to said rear rail, extendingto said front rail, and insulated from said front and rear rails;

(2) a vertical frame, having (a) a pair of vertically extending endplates,

(b) a plurality of pairs of conductive shoes, a pair of shoes beingprovided for each of said horizontal frames, one shoe of each pair beingslideably received on one of said side rails'and secured to butinsulated from one of said end plates, the other of said shoes beingslideably received on the other of said side rails and secured to butinsulated from the other of said end plates, and

(c) side plates joining but insulated from the shoes of each of saidpairs of shoes; and

(3) a plurality of resistance elements, at least one resistance elementextending between said electrically connected to the shoes of each ofsaid pairs of shoes, and being in point contact with the contact bar ofthe horizontal frame on which said shoes are received.

2. Apparatus according'to claim 1 further characterized in that saidcontact bars are pivotally connected to said rear rails.

3. Apparatus according to claim 2 further characterized in that thepivot points of said contact bars have a common vertical axis.

4. Apparatus according to claim 3 further including a verticallyextending lever secured to the forward end of each of said contact bars,said levers terminating in a common plane adjacent the upper surface ofthe assembly.

5. Apparatus according to claim 1 further including a cylindrical drumrotatably carried by each of said pairs of shoes, extending between saidpair of shoes, a plurality of said resistance elements being mounted inlongitudinal slots on the surface of said drum, the arrangement beingsuch that said drum may be rotated about its longitudinal axis to bringdifferent ones of said resistance elements into contact with saidcontact bar.

6. Apparatus according to claim 5 further including means tosimultaneously rotate each of said drums.

7. Apparatus according to claim 6 further characterized in that saidcontact bars are pivotally connected to said rear rails.

8. Apparatus according to claim 7 further characterized in that thepivot points of said contact bars have a common vertical axis.

9. Apparatus according to claim 8 further including a verticallyextending lever secured to the forward end of each of said contact bars,said levers terminating in a common plane adjacent the upper surface ofthe assembly.

References Cited UNITED STATES PATENTS 628,685 7/1899 Berresford 338-131XR 3,307,133 2/1967 Wolff 338--131 XR 3,355,694- 11/196-7 Wollf 338-428XR THOMAS J. KOZMA, Primary Examiner

